Continuous versus Intermittent Monitoring of Ventricular Rate in Patients with Permanent Atrial Fibrillation

BACKGROUND: Ventricular rate control (VRC) is an important treatment strategy for patients with permanent atrial fibrillation (AF). We assessed the prevalence of poor VRC and the adequacy of various intermittent monitoring regimens to accurately characterize VRC during permanent AF. METHODS: We retrospectively analyzed data from dual chamber implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy defibrillator (CRT-D) patients in the Medtronic Discovery™ Link having permanent AF (AF burden >23 hours/day) and ≥ 365 consecutive days of device data. Poor VRC was defined as a day with the mean ventricular rate during AF >100 beats/minute (bpm) for ICD patients and >90 bpm for CRT-D patients. Intermittent monitoring regimens were simulated from continuous device data by randomly selecting subsets of days in which data were available for analysis. Assessments of poor VRC were computed after replicating 1,000 simulations. RESULTS: ICD (n = 1,902, age = 71 ± 10) and CRT-D (n = 3,397, age = 72 ± 9) patients were included and followed for 365 days. The prevalence of poor VRC was 24.8% among ICD patients and 28.6% among CRT-D patients. Significantly more patients were identified as having poor VRC with continuous monitoring compared to all intermittent monitoring regimens (sensitivity range = 8%-31%). Furthermore, 11.6% of ICD patients and 17.9% of CRT-D patients experienced ≥ 7 days with poor VRC, to which the sensitivities of annual 7- and 21-day recordings were <7% and <20%, respectively. CONCLUSIONS: A significant proportion of permanent AF patients experience poor VRC that would be missed with random intermittent monitoring. Whether improved knowledge of VRC with continuous monitoring will lead to improved outcomes compared to intermittent monitoring requires further study.